Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 119-124).

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Scott, Waymond; Committee Member: Eslinger, Owen; Committee Member: Ingram, Mary; Committee Member: Peterson, Andrew; Committee Member: Smith, Glenn. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.S. in Engineering Science (Electrical Engineering))--Naval Postgraduate School, December 2003. / Thesis advisor(s): David Jenn, Jeffrey B. Knorr. Includes bibliographical references (p. 73-76). Also available online.

No description available.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 215-220).

No / Two novel reduced-size, printed spiral antennas are proposed for use in personal communications mobile terminals exploiting the “big low earth orbit” (Big-LEO) satellite system (uplink 1.61–1.63 GHz; downlink 2.48–2.5 GHz). The two proposed antenna give 3.12―6.25% bandwidth at lower resonant mode of 1600MHz, while at the higher resonant mode of 2450MHz a bandwidth of around 6% is obtained. The experimental and simulated return losses of the proposed antennas show good agreement. The computed and measured gains, and axial ratios are presented, showing that the performance of the proposed two antennas meets typical specifications for the intended applications.

This dissertation details the development of the star spiral antenna and demonstrates the advantages of the star spiral when used in a wideband array with variable element sizes. The wideband array with variable element sizes (WAVES) is a multi-octave array that uses different sized circular Archimedean spirals for each octave of frequency coverage. A two-octave WAVES array has been presented in the literature, but a gap in the two-octave frequency coverage exists along the principal axes. The star spiral antenna was developed to eliminate the performance gap in the WAVES array. The star spiral is a type of slow-wave spiral that also offers array-packing advantages, particularly for the WAVES array. The size reduction that can be achieved with the star spiral is comparable to that of the square spiral, but the star spiral is much more efficient in terms of its expected size reduction compared to its circumference. The far-field patterns, gain, and scan performance of the star spiral are similar to that of the circular Archimedean spiral. The use of the star spiral to eliminate the performance gap in a WAVES array of circular Archimedean spirals is detailed. Furthermore, a three-octave WAVES array of star spirals is built and measured, and the scan performance of the array is investigated via simulation. / Ph. D.

The uses for wideband antennas include wideband measurement systems, spread spectrum communications systems, feeds for reflectors and elements in wideband arrays. Here, wideband antennas are discussed and Archimedean spiral antennas are found to be appropriate elements for use in a new type of wideband array referred to as the wideband switched array. The design of an Archimedean spiral and a necessary wideband balun transformer feed structure are presented. To aid in the design, the Electromagnetic Surface Patch Code (ESP) developed by Ohio State University is used. The spiral and feed structure are constructed and measured results are compared to predictions obtained by ESP. / Master of Science

This thesis presents an analysis of the behavior of an equiangular spiral antenna using a mixture of numerical and measurement techniques. The antenna is studied as an isolated element and as a part of a spiral-based ground-penetrating radar (GPR) detection system. The numerical modeling was based on the parallelized finite-difference time-domain method and the model was validated by comparison with a prototype antenna and detection system. The intention is to isolate the effect of varying different geometrical parameters that define the spiral element or the spiral GPR system. With some notion of each parameter's effect, systems that use the spiral antenna can be designed more easily. The analysis of the spiral antenna in isolation provides a set of design graphs for the antenna. A set of design graphs are constructed that allow one to better understand the effect of the chosen dielectric substrate on the characteristic impedance of the antennas. A second set of design graphs give very specific data about the lower cut-off frequency possible for the antennas given a requirement on its minimum boresight gain, axial ratio, or voltage standing-wave ratio when matched with an appropriate transmission line. The analysis of the spiral antenna in the context of a detection system provides information on the effect of the ground on the GPR system and to what extent the circular polarization properties of the spiral antenna play a role in GPR. It is shown that a spiral antenna used in a monostatic radar configuration will reject a symmetric scatterer well into the near-field. The importance of a resistive loading to the spiral arms is demonstrated for this rejection to be optimal. In addition, it is shown that increasing the dielectric constant of the ground narrows the pattern and polarization properties, making the antenna more directive towards boresight when the spiral antennas radiate into a flat ground. In addition to this work, a method for reducing the truncation error when calculating the planewave spectrum of an antenna is described.

We developed curved spiral antennas for use in underwater (freshwater) communications. Specifically, these antennas will be integrated in so-called mussel backpacks. Backpacks are compact electronics that incorporate sensors and a small radio that operate around 300 MHz. Researchers attach these backpacks in their freshwater mussel related research. The antennas must be small, lightweight, and form-fit the mussel. Additionally, since the mussel orientation is unknown, the antennas must have broad radiation patterns. Further, the electromagnetic environment changes significantly as the mussels burrow into the river bottom. Broadband antennas, such a spiral antennas, will perform better in this instance. While spiral antennas are well established, there has been little work on their performance in freshwater. Additionally, there has been some work on curved spiral antennas, but this work focused on curving in one dimension, namely curving around a cylinder. In this thesis we develop spiral antennas that curve in two dimensions in order to conform the contour of a mussel's shell. Our research has three components, namely (a) an investigation of the relevant theoretical underpinning of spiral antennas, (b) extensive computer simulations using state-of-the art computational electromagnetics (CEM) simulation software, and (c) experimental validation. The experimental validation was performed in a large tank in a laboratory setting. We also validated some designs in a pool (∼300,000 liters of water and ∼410 squared-meter dive pool) with the aid of a certified diver. To use CEM software and perform successful antenna-related experiments require careful attention to many details. The mathematical description of radiation from an antenna, antenna input impedance and so on, is inherently complex. Engineers often make simplifying assumptions such as assuming no reflections, or an isotropic propagation environment, or operation in the antenna far field, and so on. This makes experiments on antennas challenging since it often quite difficult to replicate the simplifying assumptions in an experimental setting. Still, with careful consideration of the important factors and careful experimental design it is possible to perform successful experiments. For example, antenna measurements are often performed in anechoic chambers. For our research we used a large swimming pool to mimic an underwater anechoic chamber. Our CEM simulations and experimental results are in most cases congruent. We are confident that we can design formfitting, compact (spiral) antennas that one could deploy on mussels. This will greatly enhance the mussel backpacks that are used by researchers at the University of Iowa.